Method for cleaning reclaimed water reuse device

ABSTRACT

A method for cleaning a reclaimed water reuse device, the reclaimed water reuse device comprising a clean water supply device, a first aeration device, a backwash device and a membrane module, the method comprising detecting an operating signal of the clean water supply device; enabling the first aeration device or the backwash device according to the operating signal, so as to perform backwash of the membrane module; and completing washing back and restoring to a normal operating state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No. 11/858,921filed on Sep. 21, 2007, now U.S. Pat. No. 7,556,730, and claims prioritybenefits to Chinese Patent Application No. 200610062687.7, filed on Sep.21, 2006. The contents of all of these specifications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field biochemical engineering, andparticularly to a method for cleaning a reclaimed water reuse device.

2. Description of the Related Art

The most frequently used methods of physical cleaning include backwashand aeration. These methods need to be performed frequently and thus mayinfluence the filtering process. During backwash, permeation through themembrane is stopped momentarily. Air or water flows through themembranes in a reverse direction to physically dislodge solids off ofthe membranes. During aeration, bubbles are produced in the tank waterbelow the membranes. As the bubbles rise, they agitate or scrub themembranes and thereby dislodge some solids while creating an air lifteffect and circulation of the tank water to carry the solids away fromthe membranes. The physical cleaning requires a large amount of aerationand energy, long cleaning time, and features comparatively poor cleaningquality.

Chemical cleaning is typically performed by removing membrane modulesfrom the MBRs, and then immersing the membrane modules into a chemicalsolution. The chemical cleaning process may be complex andtime-consuming.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of theinvention to provide a method for cleaning a reclaimed water reusedevice that is simple, effective, and features good cleaning quality.

To achieve the above objective, in accordance with one aspect of thepresent invention, there is provided a method for cleaning a reclaimedwater reuse device of the invention comprising: (a) detecting anoperating signal of the clean water supply device, (b) enabling thefirst aeration device or the backwash device according to the operatingsignal, so as to perform backwash on the membrane module, and (c)completing the wash back and restoring to a normal operating state.

In certain classes of this embodiment, the reclaimed water reuse devicefurther comprises a contaminated-soil backflow device, a second aerationdevice and a control module.

In certain classes of this embodiment, the method for cleaning areclaimed water reuse device further comprises setting a timing periodand enabling the contaminated-soil backflow device when the timingperiod is up.

In certain classes of this embodiment, the step of setting a timingperiod and enabling the contaminated-soil backflow device as the timingperiod is up comprises (a) starting and entering an operating state bythe reclaimed water reuse device, (b) setting the timing period, and (c)alternately enabling the contaminated-soil backflow device and the firstaeration device and the second aeration device.

In certain classes of this embodiment, clean water supply devicecomprises a clean water supply pipe, a self-priming pump, anelectromagnetic valve, and a pressure gauge.

In certain classes of this embodiment, the step of enabling the firstaeration device or the backwash device according to the operatingsignal, so as to perform backwash on the membrane module comprises (a)setting a pressure threshold and a frequency threshold; (b) receiving apressure signal from the pressure gauge by the control module, thepressure signal indicating a self-priming pressure of the self-primingpump; (c) comparing the pressure threshold with the self-primingpressure; and (d) if the self-priming pressure exceeds the pressurethreshold, detecting whether the frequency at which the self-primingpressure of the self-priming pump exceeds the pressure threshold isgreater than the frequency threshold.

In certain classes of this embodiment, the step of enabling the firstaeration device or the backwash device according to the operatingsignal, so as to perform backwash on the membrane module furthercomprises (a) if the frequency at which the self-priming pressure of theself-priming pump exceeds the pressure threshold is greater than thefrequency threshold, performing chemical backwash of the membranemodule, and (b) if the frequency at which the self-priming pressure ofthe self-priming pump exceeds the pressure threshold is less than thefrequency threshold, enabling the first aeration device and the backwashdevice to perform physical backwash of the membrane module.

Advantages of the invention include:

(a) cleaning and regeneration of the membrane module in the membranefiltering pool can be accomplished without removing the membrane modulefrom the membrane filtering pool, which greatly simplifies an operatingprocess;

(b) while the membrane module is cleaned and regenerated, the activityin the biological reaction tank will not be affected (namely, a seamlessoperation between cleaning and normal operation is implemented), and theMBR can be restored to normal operation in a relatively short amounttime;

(c) since the invention integrates the first aeration device with thebackwash device, it is easy to apply physical (aeration) backwash,chemical backwash, or a combination thereof, to facilitate completecleaning, and to regenerate the membrane module to a great extent;therefore, the invention features simple operation and good cleaningefficiency;

(d) space separated by the separating plate forms a membrane filteringpool, which makes it applicable to all types of water processing systemssuch as normal active contaminated-soil processing device, oxidationditch processing device, contact oxidation processing device, and so on,in a cost-effective and simple manner;

(e) the contaminated-soil backflow device is connected to theinlet-drainage device, so that the high concentration contaminated soilin the membrane filtering pool is able to flow back, which reduces theconcentration of the contaminated soil, mitigates pollution of themembrane module caused by the high concentration of contaminated soil,and further improves applicability and reliability of the invention; andlastly

(f) the control module controls operating states of all devices, andthus facilitates automation of operation and standardization or MBRdevices, improves operation efficiency, and makes the inventionapplicable to large-scale production.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinafter with reference to accompanyingdrawings, in which:

FIG. 1 is a schematic diagram of a reclaimed water reuse deviceaccording to one embodiment the invention;

FIG. 2 is a block diagram of a reclaimed water reuse device according toone embodiment of the invention;

FIG. 3 is a partial enlarged view of grooves at the top of theseparating plate 5;

FIG. 4 is a high-level flowchart diagram illustrating a method forcleaning of a reclaimed water reuse device according to one embodimentof the invention; and

FIG. 5 is a detailed flowchart diagram illustrating a method forcleaning of a reclaimed water reuse device according to one embodimentof the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Detailed description will be given below in conjunction with accompanydrawings.

As shown in FIGS. 1 and 2, a reclaimed water reuse device of theinvention comprises a biological reaction tank 1, a membrane module 2, awater pool 3, a membrane filtering pool 4, a control module 6, aninlet-drainage device 11, a clean water supply device 21, an outletdevice 31, a first aeration device 22, a second aeration device 12, abackwash device 23, and a contaminated-soil backflow device 41.

The membrane module 2 is disposed in the membrane filtering pool 4.

A separating plate 5 is disposed in the biological reaction tank 1, andseparates the membrane filtering pool 4 from the biological reactiontank 1. Water in the biological reaction tank 1 overflows a top of theseparating plate 5 and pours into the membrane filtering pool 4. Theratio between the volume of the biological reaction tank 1 and that ofthe membrane filtering pool 4 is between 1:1 and 10:1, and moreparticularly, the ratio is 3:1.

A groove 51 is disposed at the top of the separating plate 5. In thisembodiment, the groove 51 is tooth-shaped.

The inlet-drainage device 11 comprises an inlet pipe 111, a drainagepipe 112, and a plurality of electromagnetic valves M0 and M1. Theelectromagnetic valve M0 is disposed in the inlet pipe 111, and theelectromagnetic valve M1 is disposed in the drainage pipe 112.

The outlet device 31 drains water from the water pool 3. The outletdevice 31 comprises an outlet pipe 311, a clean water pump 312, and anelectromagnetic valve M9. The clean water pump 312 and theelectromagnetic valve M9 are attached to the outlet pipe 311.

The clean water supply device 21 comprises a clean water supply pipe211, a self-priming pump 212, an electromagnetic valve M8, a manualvalve H8, and a pressure gauge P. The clean water supply pipe 211connects the water pool 3 to the membrane module 2. The self-primingpump 212, the electromagnetic valve M8, the manual valve H8, and thepressure gauge P are connected to the clean water supply pipe 211 anddisposed between the membrane module 2 and the water pool 3. Thepressure gauge P detects self-priming pressure of the self-priming pump212, and transfers the pressure signal to the control module 6.

The first aeration device 22 aerates the membrane module 2, andcomprises a first aeration pipe 221, an electromagnetic valve M5 and amanual valve H5. The electromagnetic valve M5 and the manual valve H5are connected to the first aeration pipe 221. The first aeration pipe221 extends to the bottom of the membrane module 2.

The second aeration device 12 aerates the biological reaction tank 1,and comprises a second aeration pipe 121, an electromagnetic valve M3and a manual valve H3. The electromagnetic valve M3 and the manual valveH3 are connected to the second aeration pipe 121. The second aerationpipe 121 extends to the bottom of the biological reaction tank 1.

The aeration pipe 221 and the second aeration pipe 121 have a commonentrance.

The backwash device 23 washes back the membrane filtering pool 4 andconnects the outlet device 31 to the membrane module 2.

The backwash device 23 comprises a backwash pipe 231, a first backwashsupporting pipe 232, a second backwash supporting pipe 233,electromagnetic valves M6 and M7, and a manual valve H6.

One end of the backwash pipe 231 is connected to the outlet pipe 311,and the other end of the backwash pipe 231 is a common end of the firstbackwash supporting pipe 232 and the second backwash supporting pipe233. The first backwash supporting pipe 232 is, at its other end,disposed in the membrane filtering pool 4. The second backwashsupporting pipe 233 and the clean water supply pipe 211 are connected tothe membrane module 2

The electromagnetic valve M6 is connected to the first backwashsupporting pipe 232, and the electromagnetic valve M7 is connected tothe second backwash supporting pipe 233.

The contaminated-soil backflow device 41 is disposed in the membranefiltering pool 4, and is connected to the inlet-drainage device 11 andthe biological reaction tank 1.

The contaminated-soil backflow device 41 comprises a backflow pipe 411,a first backflow supporting pipe 412, a second backflow supporting pipe413, a backflow pump 414, and electromagnetic valves M2 and M4.

The backflow pump 414 is disposed at the bottom of the membranefiltering pool 4, and connected to one end of the backflow pipe 411. Theother end of the backflow pipe 411 is a common end of the first backflowsupporting pipe 412 and the second backflow supporting pipe 413. Thefirst backflow supporting pipe 412 terminates at the top of thebiological reaction tank 1, and the second backflow supporting pipe 413is connected to the outlet pipe 112.

The electromagnetic valve M4 is connected to the first backflowsupporting pipe 412, and the electromagnetic valve M2 is connected tothe second backflow supporting pipe 413.

As shown in FIG. 2, the control module 6 controls operation of theinlet-drainage device 11, the clean water supply device 21, the outletdevice 31, the first aeration device 22, the backwash device 23, thecontaminated-soil backflow device 41, and the clean water supply device21 according to preset data and/or signal received from the clean watersupply device 21. The preset data comprises a timing period T0, a delaytime T1, a pressure threshold F1, a frequency threshold f1, and so on.The operating signal of the clean water supply device 21 comprises apressure signal of the pressure gauge P, etc. Based on the pressuresignal, the control module 6 detects the operating state of the membranemodule 2, and correspondingly performs physical or chemical backwash ofthe membrane module 2.

Referring to FIG. 2, the control module 6 directly controls operatingstates of the electromagnetic valves M0 . . . M9, the self-priming pump212, the clean water pump 312, and the backflow pump 414.

As the reclaimed water reuse device of the invention is in a normaloperating state, the backflow pump 414, the self-priming pump 212, theclean water pump 312, and the electromagnetic valves M4, M3, M5, M8 andM9 are enabled; the other valves are disabled. Manual valves H3, H5 andH6 may be manually adjusted to change gas flux and water flux. Duringnormal operation, contaminated water flows in via the inlet pipe 111,after biological processing and being filtered by the membrane module 2in the membrane filtering pool 4, clean water is generated.

As shown in FIG. 4, a method for cleaning a reclaimed water reuse devicecomprises the following steps:

-   -   i. The reclaimed water reuse device is enabled, and enters a        normal operating state;    -   ii. A timing period T0 is set, and saved in the control module        6;    -   iii. As the timing period T0 is up, the reclaimed water reuse        device is disabled; after a delay time T1, the control module 6        enables the contaminated-soil backflow device 41, so that        contaminated soil deposited at the bottom of the membrane        filtering pool 4 flows back to a front portion of the biological        reaction tank 1;    -   iv. The control module 6 detects an operating signal of the        clean water supply device 21, and enables the first aeration        device 22 or/and the backwash device 23 according to the        operating signal, so as to perform physical or chemical backwash        of the membrane module 2; and    -   v. After the backwash is completed, the reclaimed water reuse        device restores to a normal operating state under the control of        the control module 6, and the process returns to step iii.

As shown in FIG. 5, a detailed method for cleaning a reclaimed waterreuse device comprises the following steps:

-   -   1. The reclaimed water reuse device is enabled, and enters a        normal operating state;    -   2. A timing period T0 is set, and saved in the control module 6;    -   3. The control module 6 detects whether the timing period is up,        if the timing period is not up, the process proceeds to step 4,        otherwise the process proceeds to step 9;    -   4. If the timing period is up, the control module 6 detects        whether contaminated-soil backflow is enabled. In this        embodiment, the control module 6 detects whether        contaminated-soil backflow is enabled by checking the signal        from the backwash pump 414, or an operating history saved in the        control module 6. If the contaminated-soil backflow is enabled,        the process proceeds to step 5, otherwise the process proceeds        to step 6;    -   5. After a deposit time T1, the control module 6 stops the        contaminated-soil backflow and starts aeration. In this        embodiment, the control module 6 switches on the electromagnetic        valve M5 in the first aeration device 22 and the electromagnetic        valve M3 in the second aeration device 12, so that gas is led to        the bottom of the membrane module 2 and the biological reaction        tank 1 via the first aeration pipe 221 and the second aeration        pipe 121, respectively;    -   6. The control module 6 detects whether aeration is enabled. In        this embodiment, the control module 6 detects whether aeration        is enabled by checking states of the electromagnetic valve M5        and the electromagnetic valve M3. If the aeration is enabled,        the process proceeds to step 7, otherwise the process proceeds        to step 8;    -   7. The control module 6 stops the aeration, and enables the        contaminated-soil backflow after the deposit time T1;    -   8. The control module 6 enables the contaminated-soil backflow        after the deposit time T1;    -   9. The control module 6 sets a pressure threshold F1 and a        frequency threshold f1. In this embodiment, the pressure        threshold F1 is between +0.04 and −0.04 MPa with respect to the        standard pressure of 760 mmHg (101,325 Pa).    -   10. The control module 6 receives a pressure signal from the        pressure gauge P, the pressure gauge indicating self-priming        pressure of the self-priming pump 212;    -   11. The control module 6 detects whether the self-priming        pressure is greater than the pressure threshold F1. If the        self-priming pressure is greater than the pressure threshold F1,        the process proceeds to step 12, otherwise the process returns        to step 3;    -   12. The control module 6 detects whether a frequency at which        the self-priming pressure of the self-priming pump 212 exceeds        the pressure threshold F1 is greater than the frequency        threshold f1. If the frequency at which the self-priming        pressure of the self-priming pump 212 exceeds the pressure        threshold F1 is greater than the frequency threshold f1, the        process proceeds to step 13, otherwise the process proceeds to        step 14. In this embodiment, the frequency at which the        self-priming pressure of the self-priming pump 212 exceeds the        pressure threshold F1 is equal to 1/(the amount of time the        self-priming pressure of the self-priming pump 212 exceeds the        pressure threshold F1 during this time interval−the amount of        time the self-priming pressure of the self-priming pump 212        exceeds the pressure threshold F1 during the immediately        preceding time interval);    -   13. the control module 6 exits the normal operating state, and        performs chemical backwash on the membrane module 2;    -   14. The control module 6 exits the normal operating state, and        enables the first aeration device 22 and the backwash device 23,        so as to perform physical backwash on the membrane module 2; and    -   15. Under the control of the control module 6, the reclaimed        water reuse device is restored to its normal operating state,        and then the process returns to step 3.

The above steps 4-7 alternately enable contaminated-soil backflow andaeration. The above steps 10-14 implement combination of the physicalbackwash and the chemical backwash. The membrane module 2 is notrequired to be taken out of the membrane filtering pool 4 for cleaning.All of this contributes to a good cleaning efficiency.

A detailed process of the physical backwash is as follows: the controlmodule 6 enables the electromagnetic valves M5 and M7 and the cleanwater pump 312, the clean water pump 312 pours filtered water into amembrane tube and a membrane hole in the membrane module 2, so as toperform backwash thereon. Meanwhile, blowing aeration is performed atthe bottom of the membrane module 2, and contaminant deposited on anupper surface of the membrane module 2 is cleaned. The entire processlasts for 2-10 minutes.

A detailed process of the chemical backwash is as follows: cleaningchemical agent such as acid, alkali, oxidant (sodium hypochlorite) andso on is added to the water pool 3, and let the biological reaction tank1 and the membrane filtering pool 4 stands for 5-15 minutes. In thisembodiment, the soaking time is 10 minutes. The control module 6 enablesthe electromagnetic valve M1 to drain clean water from the upper portionof the biological reaction tank 1. And then disables the electromagneticvalve M1.

The control module 6 enables the contaminated-soil backflow pump 414 andthe electromagnetic valve M4, so that active contaminated soil in themembrane filtering pool 4 flows back to the biological reaction tank 1.

The control module 6 disables the electromagnetic valve M4 and enablesthe electromagnetic valve M2 after the backflow is completed, so as todischarge clean water in the upper portion of the membrane filteringpool 4 to outside via the contaminated-soil backflow pump 414.

The control module 6 disables the contaminated-soil backflow pump 414after the membrane filtering pool 4 is evacuated.

The control module 6 enables the clean water pump 312 and theelectromagnetic valve M6, and allows the cleaning chemical agent to flowinto the membrane filtering pool 4, so as to immerse the membrane module2.

The control module 6 disables the electromagnetic valve M6 after thecleaning chemical agent immerses the membrane module 2, enables theelectromagnetic valves M5 and M7, and performs chemical backwash on themembrane module 2. Meanwhile, a membrane surface is scrubbed viaaeration.

The control module 6 disables the electromagnetic valves M5 and M7 andthe clean water pump 312, enables the contaminated-soil backflow pump414 and the electromagnetic valve M2, so as to evacuate the cleaningchemical agent in the membrane filtering pool 4, and then disables thecontaminated-soil backflow pump 414 and the electromagnetic valve M2.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and therefore, the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

1. A method for cleaning a reclaimed water reuse device, the reclaimedwater reuse device comprising a clean water supply device, a firstaeration device, a backwash device and a membrane module, the methodcomprising (a) detecting an operating signal of said clean water supplydevice; (b) enabling said first aeration device or said backwash deviceaccording to said operating signal, so as to perform backwash of saidmembrane module; and (c) completing washing back and restoring to anormal operating state.
 2. The method of claim 1, wherein said reclaimedwater reuse device further comprises a contaminated-soil backflowdevice, a second aeration device and a control module.
 3. The method ofclaim 2, further comprising setting a timing period and enabling saidcontaminated-soil backflow device when said timing period is up.
 4. Themethod of claim 3, wherein the step of setting a timing period andenabling said contaminated-soil backflow device as said timing period isup comprises: (a) starting and entering an operating state by saidreclaimed water reuse device; (b) setting said timing period; and (c)alternately enabling said contaminated-soil backflow device, said firstaeration device and said second aeration device.
 5. The method of claim2, wherein said clean water supply device comprises a clean water supplydevice, a self-priming pump, an electromagnetic valve, and a pressuregauge.
 6. The method of claim 5, wherein the step of enabling said firstaeration device or said backwash device according to said operatingsignal, so as to perform backwash on said membrane module comprises (a)setting a pressure threshold and a frequency threshold; (b) receiving apressure signal from said pressure gauge by said control module, thepressure signal indicating a self-priming pressure of said self-primingpump; (c) comparing said pressure threshold with said self-primingpressure; and (d) if said pressure threshold is less than saidself-priming pressure, detecting whether the frequency at which theself-priming pressure of said self-priming pump exceeds said pressurethreshold is greater than said frequency threshold.
 7. The method ofclaim 6, wherein the step of enabling said first aeration device or saidbackwash device according to said operating signal, so as to performbackwash on said membrane module further comprises (a) if the frequencyat which the self-priming pressure of said self-priming pump exceedssaid pressure threshold is greater than said frequency threshold,performing chemical backwash on said membrane module; and (b) if thefrequency at which the self-priming pressure of said self-priming pumpexceeds said pressure threshold is less than said frequency threshold,enabling said first aeration device and said backwash device to performphysical backwash of said membrane module.
 8. A method for cleaning areclaimed water reuse device, the reclaimed water reuse devicecomprising a biological reaction tank; a membrane module; a water pool;an inlet-drainage device; an outlet device; a clean water supply device;a first aeration device; a backwash device; and a membrane filteringpool; wherein said inlet-drainage device has the ability to feed waterinto and drain water from said biological reaction tank; said cleanwater supply device has the ability to supply clean water from saidmembrane module to said water pool; said first aeration device has theability to clean said membrane module; said membrane module is disposedin said membrane filtering pool; said backwash device is connected tosaid membrane module via said outlet device; and said backwash devicehas the ability to wash back said membrane filtering pool; the methodcomprising: (a) detecting an operating signal of said clean water supplydevice; (b) enabling said first aeration device or said backwash deviceaccording to said operating signal, so as to perform backwash of saidmembrane module; and (c) completing washing back and restoring to anormal operating state.
 9. The method of claim 8, wherein said reclaimedwater reuse device further comprises a contaminated-soil backflowdevice, a second aeration device and a control module.
 10. The method ofclaim 9, further comprising setting a timing period and enabling saidcontaminated-soil backflow device when said timing period is up.
 11. Themethod of claim 10, wherein the step of setting a timing period andenabling said contaminated-soil backflow device as said timing period isup comprises: (a) starting and entering an operating state by saidreclaimed water reuse device; (b) setting said timing period; and (c)alternately enabling said contaminated-soil backflow device, said firstaeration device and said second aeration device.
 12. The method of claim9, wherein said clean water supply device comprises a clean water supplydevice, a self-priming pump, an electromagnetic valve, and a pressuregauge.
 13. The method of claim 12, wherein the step of enabling saidfirst aeration device or said backwash device according to saidoperating signal, so as to perform backwash on said membrane modulecomprises (a) setting a pressure threshold and a frequency threshold;(b) receiving a pressure signal from said pressure gauge by said controlmodule, the pressure signal indicating a self-priming pressure of saidself-priming pump; (c) comparing said pressure threshold with saidself-priming pressure; and (d) if said pressure threshold is less thansaid self-priming pressure, detecting whether the frequency at which theself-priming pressure of said self-priming pump exceeds said pressurethreshold is greater than said frequency threshold.
 14. The method ofclaim 13, wherein the step of enabling said first aeration device orsaid backwash device according to said operating signal, so as toperform backwash on said membrane module further comprises (a) if thefrequency at which the self-priming pressure of said self-priming pumpexceeds said pressure threshold is greater than said frequencythreshold, performing chemical backwash on said membrane module; and (b)if the frequency at which the self-priming pressure of said self-primingpump exceeds said pressure threshold is less than said frequencythreshold, enabling said first aeration device and said backwash deviceto perform physical backwash of said membrane module.